首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2567篇
  免费   135篇
  国内免费   258篇
化学   24篇
晶体学   1篇
力学   85篇
综合类   47篇
数学   2711篇
物理学   92篇
  2023年   14篇
  2022年   11篇
  2021年   26篇
  2020年   32篇
  2019年   47篇
  2018年   43篇
  2017年   65篇
  2016年   70篇
  2015年   56篇
  2014年   91篇
  2013年   127篇
  2012年   129篇
  2011年   91篇
  2010年   83篇
  2009年   128篇
  2008年   139篇
  2007年   173篇
  2006年   160篇
  2005年   144篇
  2004年   133篇
  2003年   121篇
  2002年   118篇
  2001年   103篇
  2000年   137篇
  1999年   95篇
  1998年   101篇
  1997年   109篇
  1996年   54篇
  1995年   46篇
  1994年   41篇
  1993年   39篇
  1992年   28篇
  1991年   26篇
  1990年   24篇
  1989年   10篇
  1988年   16篇
  1987年   13篇
  1986年   7篇
  1985年   14篇
  1984年   14篇
  1983年   5篇
  1982年   11篇
  1981年   13篇
  1980年   9篇
  1979年   9篇
  1978年   10篇
  1977年   9篇
  1976年   3篇
  1975年   2篇
  1974年   6篇
排序方式: 共有2960条查询结果,搜索用时 15 毫秒
31.
This is the first part of a work on second order nonlinear, nonmonotone evolution inclusions defined in the framework of an evolution triple of spaces and with a multivalued nonlinearity depending on both x(t) and x(t). In this first part we prove existence and relaxation theorems. We consider the case of an usc, convex valued nonlinearity and we show that for this problem the solution set is nonempty and compact in C^1 (T, H). Also we examine the Isc, nonconvex case and again we prove the existence of solutions. In addition we establish the existence of extremal solutions and by strengthening our hypotheses, we show that the extremal solutions are dense in C^1 (T, H) to the solutions of the original convex problem (strong relaxation). An example of a nonlinear hyperbolic optimal control problem is also discussed.  相似文献   
32.
梁俊奇  张志宏  赵玲 《数学季刊》2003,18(3):264-270
§ 1. Introduction  Anecessaryandsufficientconditionandasufficientconditiontoensurethataset valuedmappingandasingle valuedmappinginacompletemetricspaceandacompleteconvexmetricspacehavingacommonfixedpointarerespectivelygivenin [1 ] .Meanwhilethemainresultsin[2 ]— [5]areimprovedandextendedin [1 ] .Inthispaper ,theexistenceatcommonfixedpointsoftwoset valuedmappingandasing valuedmappingwerestudied ,andthecorrespond ingresultsin [1 ]— [5]wereextendedandimproved .Let(X ,d)beanon emptymetricspa…  相似文献   
33.
几何凸函数与琴生型不等式   总被引:20,自引:3,他引:17  
给出几何凸函数的定义以及判定几何凸函数的方法 ,建立关于几何凸函数的琴生型不等式 ,最后给出它的应用 ,包括改进一些已知不等式和建立一些新不等式 .  相似文献   
34.
In this paper we provide an extension of barycentric coordinates from simplices to arbitrary convex sets. Barycentric coordinates over convex 2D polygons have found numerous applications in various fields as they allow smooth interpolation of data located on vertices. However, no explicit formulation valid for arbitrary convex polytopes has been proposed to extend this interpolation in higher dimensions. Moreover, there has been no attempt to extend these functions into the continuous domain, where barycentric coordinates are related to Green’s functions and construct functions that satisfy a boundary value problem. First, we review the properties and construction of barycentric coordinates in the discrete domain for convex polytopes. Next, we show how these concepts extend into the continuous domain to yield barycentric coordinates for continuous functions. We then provide a proof that our functions satisfy all the desirable properties of barycentric coordinates in arbitrary dimensions. Finally, we provide an example of constructing such barycentric functions over regions bounded by parametric curves and show how they can be used to perform freeform deformations.   相似文献   
35.
The existence of global error bound for convex inclusion problems is discussed in this paper, including pointwise global error bound and uniform global error bound. The existence of uniform global error bound has been carefully studied in Burke and Tseng (SIAM J. Optim. 6(2), 265–282, 1996) which unifies and extends many existing results. Our results on the uniform global error bound (see Theorem 3.2) generalize Theorem 9 in Burke and Tseng (1996) by weakening the constraint qualification and by widening the varying range of the parameter. As an application, the existence of global error bound for convex multifunctions is also discussed.  相似文献   
36.
THENBELCANDNWELCCLASSESOFLIFEDISTRIBUTIONS¥CAOJINHUA;WANGYUEDONG(InstituteofAppliedMathematics,ChineseAcademyofScience,Beijin...  相似文献   
37.
A BRANCH BOUND METHOD FOR SUBSET SUM PROBLEM   总被引:1,自引:0,他引:1  
ABRANCHBOUNDMETHODFORSUBSETSUMPROBLEMWUSHIQUAN(吴士泉)(InstituteofAppliedMathematics,theChineseAcademyofSciences,Beijing100080,C...  相似文献   
38.
A primal-dual version of the proximal point algorithm is developed for linearly constrained convex programming problems. The algorithm is an iterative method to find a saddle point of the Lagrangian of the problem. At each iteration of the algorithm, we compute an approximate saddle point of the Lagrangian function augmented by quadratic proximal terms of both primal and dual variables. Specifically, we first minimize the function with respect to the primal variables and then approximately maximize the resulting function of the dual variables. The merit of this approach exists in the fact that the latter function is differentiable and the maximization of this function is subject to no constraints. We discuss convergence properties of the algorithm and report some numerical results for network flow problems with separable quadratic costs.  相似文献   
39.
黎奇升  佟文廷 《数学进展》2004,33(2):236-242
本文证明了:(1)Exchange环R的K0群的正向凸子群格同构于R的稳定余有限半本原理想格;(2)稳定有限、半本原的exchange环R是单的当且仅当它是K0-单的并且满足逼近弱s^*—可比性,推广了Goodearl,Ara等人的结果。  相似文献   
40.
We propose general variational inclusion problems which are slightly different from corresponding problems considered in several recent papers in the literature and show that they are advantageous. Sufficient conditions for the solution existence are established. As applications we derive consequences for several special cases of variational inclusion problems, quasioptimization problems, equilibrium problems and implicit variational inequalities and show that they improve the results of some recent existing papers.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号